The major goal of this project is to develop new ligands for receptors and ion channels using biologically active peptides from two cone snail venoms, Conus textile and Conus radiatus. Our interest in Conus radiatus venom is in peptide probes which have NMDA antagonist activity; preliminary data suggest five candidate peptides. We are carrying out an extensive characterization of biologically active peptides in Conus textile venom because we feel that many of these will serve as useful molecular probes for key invertebrate nervous systems. Initially, two novel peptides in Conus textile venom that elicit specific behavioral symptoms analogous to the behavior of mutant mice deficient in glycine receptors. The second is the "King-Kong" peptide which makes lobsters assume a dominant posture even in the presence of bigger lobsters. Both peptides are 27 amino acids long and contain 6 residues of cysteine. Peptide will be chemically synthesized and the physiological activity of each peptide will be examined. Radiolabeled derivatives of the peptides will be made and used as probes for their receptor targets. Recently, cDNA clones of the King-Kong peptide were isolated. However, of 15 clones sequenced, a family of transcripts encoding three different propeptides was revealed. When the three propeptide sequences are aligned, highly conserved and hypervariable regions can be defined. The N-terminal excised region and the 6 cysteine residues in the final peptide comprise the constant region; the intercysteine segments are the hypervariable regions. We will test whether an N-terminal excised region can be correlated to the disulfide bonded framework of a Conus peptide. The combination of biochemical and cloning techniques provides a powerful tool for the analysis of peptides from Conus venom, and their development as tools in neurobiology.